TY - JOUR

T1 - A Monolayer Carbon Nitride on Au(111) with a High Density of Single Co Sites

AU - Gammelgaard, Jens Jakob

AU - Sun, Zhaozong

AU - Vestergaard, Anders K.

AU - Zhao, Siqi

AU - Li, Zheshen

AU - Lock, Nina

AU - Daasbjerg, Kim

AU - Bagger, Alexander

AU - Rossmeisl, Jan

AU - Lauritsen, Jeppe V.

N1 - Funding Information: J.V.L. and J.R. acknowledge funding from Independent Research Fund Denmark (IRFD 0217-00014B). A.B. and J.R. acknowledge the Danish National Research Foundation Center for High Entropy Alloy Catalysis (DNRF 149). A.B. acknowledges support from the Carlsberg Foundation (CF21-0144). J.V.L. acknowledges Integrated Materials Research Center (iMAT) at Aarhus University and funding from the SMART Lighthouse. K.D. and S.Z. acknowledge support by the Novo Nordisk Foundation CO2 Research Center (Grant no. NNF21SA0072700). We acknowledge the MAX IV Laboratory for time on Beamline FlexPES and the STM Laboratory under proposal 20210259, and FlexPES under proposal 20220531. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496. We acknowledge beam time received at ASTRID2 on the MATLine beamline. Funding Information: J.V.L. and J.R. acknowledge funding from Independent Research Fund Denmark (IRFD 0217-00014B). A.B. and J.R. acknowledge the Danish National Research Foundation Center for High Entropy Alloy Catalysis (DNRF 149). A.B. acknowledges support from the Carlsberg Foundation (CF21-0144). J.V.L. acknowledges Integrated Materials Research Center (iMAT) at Aarhus University and funding from the SMART Lighthouse. K.D. and S.Z. acknowledge support by the Novo Nordisk Foundation CO Research Center (Grant no. NNF21SA0072700). We acknowledge the MAX IV Laboratory for time on Beamline FlexPES and the STM Laboratory under proposal 20210259, and FlexPES under proposal 20220531. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496. We acknowledge beam time received at ASTRID2 on the MATLine beamline. 2 Publisher Copyright: © 2023 American Chemical Society.

PY - 2023

Y1 - 2023

N2 - Carbon nitrides that expose atomically dispersed single-atom metals in the form of M-N-C (M = metal) sites are attractive earth-abundant catalyst materials that have been demonstrated in electrocatalytic conversion reactions. The catalytic performance is determined by the abundance of N-doped sites and the type of metal coordination to N, but challenges remain to synthesize pristine carbon nitrides with a high concentration of the most active sites and prepare homogeneously doped materials that allow for in-depth characterization of the M-N-C sites and quantitative evaluation of their catalytic performance. Herein, we have synthesized and characterized a well-defined monolayer carbon nitride phase on a Au(111) surface that exposes an exceedingly high concentration of Co-N4 sites. The crystalline monolayer carbon nitride, whose formation is controlled by an on-surface reaction between Co atoms and melamine on Au(111), is characterized by a dense array of 4- and 6-fold N-terminated pockets, whereof only the 4-fold pocket is found to be holding Co atoms. Through detailed characterization using scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory modeling, we determine the atomic structure and chemical state of the carbon nitride network. Furthermore, we show that the monolayer carbon nitride structure is stable and reactive toward the electrocatalytic oxygen reduction reaction in alkaline electrolyte, with a quantitative performance metric that significantly exceeds comparable M-N-C-based catalyst types. The work demonstrates that high-density active catalytic sites can be created using common precursor materials, and the formed networks themselves offer an excellent platform for onward studies addressing the characteristics of M-N-C sites.

AB - Carbon nitrides that expose atomically dispersed single-atom metals in the form of M-N-C (M = metal) sites are attractive earth-abundant catalyst materials that have been demonstrated in electrocatalytic conversion reactions. The catalytic performance is determined by the abundance of N-doped sites and the type of metal coordination to N, but challenges remain to synthesize pristine carbon nitrides with a high concentration of the most active sites and prepare homogeneously doped materials that allow for in-depth characterization of the M-N-C sites and quantitative evaluation of their catalytic performance. Herein, we have synthesized and characterized a well-defined monolayer carbon nitride phase on a Au(111) surface that exposes an exceedingly high concentration of Co-N4 sites. The crystalline monolayer carbon nitride, whose formation is controlled by an on-surface reaction between Co atoms and melamine on Au(111), is characterized by a dense array of 4- and 6-fold N-terminated pockets, whereof only the 4-fold pocket is found to be holding Co atoms. Through detailed characterization using scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory modeling, we determine the atomic structure and chemical state of the carbon nitride network. Furthermore, we show that the monolayer carbon nitride structure is stable and reactive toward the electrocatalytic oxygen reduction reaction in alkaline electrolyte, with a quantitative performance metric that significantly exceeds comparable M-N-C-based catalyst types. The work demonstrates that high-density active catalytic sites can be created using common precursor materials, and the formed networks themselves offer an excellent platform for onward studies addressing the characteristics of M-N-C sites.

KW - density functional theory

KW - on-surface synthesis

KW - oxygen reduction reaction

KW - scanning tunneling microscopy

KW - single-atom catalysis

KW - X-ray photoelectron spectroscopy

U2 - 10.1021/acsnano.3c05996

DO - 10.1021/acsnano.3c05996

M3 - Journal article

C2 - 37643209

AN - SCOPUS:85171202922

VL - 17

SP - 17489

EP - 17498

JO - A C S Nano

JF - A C S Nano

SN - 1936-0851

IS - 17

ER -